Generally, a vehicle nowadays has many electronic control units installed therein, and, among those electronic control units (ECUs), some have a self-diagnosis function for diagnosing an abnormality of the vehicle, which may be designated as On-Board Diagnostics (OBD). In recent years, OBD II standard is enacted, which is applicable to most of gasoline-engine vehicles and diesel-engine vehicles. According to the OBD II standard, the abnormality of the vehicle and the parts are diagnosable based on a regular monitoring of critical components and other conditions, such as an engine, an exhaust gas and the like.
The ECU stores information indicative of abnormality of a vehicle to a memory unit when diagnosis items are diagnosed as abnormal based on information of various sensors that are installed in a vehicle, which is then read out by a mechanic in charge by using an external device at a vehicle dealer, at a factory or the like. The read-out information is utilized for many purposes such as a repair of the vehicle, a replacement of the parts, or the like. See for example a patent document, Japanese Patent Laid-Open No. 2011-255862 (patent document 1).
When the self-diagnosis function is not properly functioning for some reasons, the abnormality of sensors or the like is not appropriately diagnosable. Therefore, the function of the abnormal sensor is configured to also be diagnosable as is (i.e., with the sensor being in an installed state in the vehicle), from an outside of the vehicle by using an external device or the like, and a state of performing the abnormality diagnosis of the sensors and other devices are stored in a memory unit.
For example, according to the OBD II standard, the abnormality diagnosis determination items and the abnormality diagnosis inspection items (i.e., designated as abnormality diagnosis items hereafter) are stored as readiness information in the memory unit when satisfied. In other words, when all items of the readiness information are stored as satisfied, the vehicle is shippable from a factory, or is returnable to a user from a repair shop or from a vehicle dealer.
The readiness information is erasable (i.e., completely cleared, or “all-cleared”) by the external device (i.e., by a scan tool), according to the OBD II standard, which means the information is erasable/may be deleted from the memory unit. However, the readiness information is considered as complete only after all abnormality diagnosis items are satisfied. The ease of satisfying an abnormality diagnosis item is different from item to item, and the time required for the determination of the respective diagnosis items also varies from item to item. In other words, a certain diagnosis item may take a very long time to be determined as satisfied once the readiness information about such an item is cleared. Therefore, especially when ECU receives an all clear request for clearing readiness from the external scan tool in a shipping process of a factory or in a repair process of a vehicle dealer, such an all clear request must be appropriately handled.